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Comparative physiology of Mycobacterium abscessus in synthetic laboratory medium and cystic fibrosis sputum




Wiersma, Crystal J., author
Jackson, Mary, advisor
Borlee, Bradley, committee member
Jahn, Courtney, committee member

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Mycobacterium abscessus complex is a group of rapid-growing nontuberculous mycobacteria that are multidrug resistant and that cause chronic pulmonary infections in individuals with cystic fibrosis (CF) and other pre-disposing conditions. Research progress is challenged by the lack of laboratory models that mimic the lung environment, a nutritionally complex environment not well represented by current laboratory medium. In this study, the growth characteristics and gene expression profile of a diverse panel of M. abscessus isolates were characterized and compared when grown in 7H9 Middlebrook medium (a synthetic Mycobacterium laboratory culture medium); Synthetic Cystic Fibrosis Medium 2 (SCFM2), a medium which mimics the composition of CF sputum; and actual patient CF sputum. Tests were also performed measuring the antibiotic susceptibility and characterizing the cell envelope composition of the M. abscessus isolates in these media. Although the medium composition did not affect the antibiotic susceptibility or growth of the isolates, it caused changes in fatty acid and outer membrane lipid compositions which may account, at least in part, for observed differences in the subsequent infectivity of the isolates inside macrophages and epithelial cells. The gene expression profiles showed similar upregulation of pathways related to carbon metabolism for Mycobacterium abscessus grown in SCFM2 and grown in CF sputum while reaffirming the complexity of CF sputum and the many metabolic and structural adaptations that M. abscessus undergoes during growth in varied environments.


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cystic fibrosis


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